Class-D audio amplifiers are often used for audio amplification because of their power efficiency. Typically, the Class D audio amplifier is operated in switch mode with minimized internal power consumption. The so-called “Bang-Bang” type control has improved the loop response and simplified the feedback loop control. This type of control is useful for a single-ended amplifier, which is shown in FIG. 1. The amplifier's output is connected to an LC filter, and then fed to a speaker through a large DC-blocking capacitor(s). In steady state operation, if the SW node is high, the voltage on the Cint and Vcin will increase gradually. After a certain time t1, the Vcin increases beyond the hysteresis of the comparator and causes the comparator to switch state and the SW node to switch from high to low. C2 provides an additional feedback from the speaker output and helps to improve the transient response. The method can help audio amplifiers achieve superior transient response and thus minimize the switching frequency and its related switching losses. In addition, the method varies the switching frequency and helps to suppress the amplitude of electric-magnetic interference (EMI) noises. However, the output signal amplitude from this method can only be up to half of the supply voltage and its output power is limited.
For higher power applications, it is desirable to have the amplifier's output signal reach full supply voltage.